I looked up twig in a slang dictionary. There was no notation that it was British. I have never heard twig used as a slang word. There used to be a British "model?" who was named Twiggy because she was so thin. Only some of the elderly set on this forum remember Twiggy. She didn't last long as a topic of conversation or as a model.

With all the recent reading I have done on the simple word "twig", I could probably write a dissertation worthy of a PhD. I had no idea past twig being identical in meaning to the German cognate Zweig. Now I find that twig, in the sense of learn or catch on, is a word and is not a slang word. It has an extensive history and an etymology from the Celtic languages. At my advanced age it seems I still don't know my native language. Slava, thanks for clueing us in.